Compact linear Fresnel reflector

December 6, 2017
by Webmaster
8 min read

A linear linear Fresnel reflector ( CLFR ) – also referred to as a concentrating linear Fresnel reflector – is a specific type of linear Fresnel reflector ( LFR ) technology. Linear Fresnel reflectors use long, thin segments of mirrors to focus sunlight onto a fixed absorbed at a common focal point of the reflectors. These mirrors are capable of concentrating the sun’s energy to approximately 30 times its normal intensity . [1] This concentrated energy is absorbed by the absorbent of some thermal fluid (this is typically oil capable of maintaining liquid state at very high temperatures). The fluid then goes through a heat exchangerto power a steam generator . As opposed to traditional LFRs, the CLFR uses multiple absorbers within the vicinity of the mirrors.

History

The first linear Fresnel reflector solar power system was developed in Italy in 1961 by Giovanni Francia of the University of Genoa . [2] Francia demonstrated that such a system could create elevated temperatures capable of making a fluid do work. The technology was further investigated by the FMC Corporation during the 1973 oil crisis , but remained relatively untouched until the early 1990s. [1] In 1993, the first CLFR was developed at the University of Sydney in 1993 and patented in 1995. In 1999, the CLFR design was enhanced by the introduction of the advanced absorb. [2] In 2003 the concept was extended to3D geometry. [3] Research published in 2010 Showed That Higher concentrations and / or Higher acceptance angles Could Be Obtained by using nonimaging optics [4] to explore different degrees of freedom in the system Such As varying, the size and curvature of the heliostats , Placing Them at a varying height (on a wave-shape curve) and combining the result with nonimaging secondaries. [5]

Design

Reflectors

The reflectors are located at the base of the system and converge the sun’s rays to absorb. A key component that makes all LFRs more effective than traditional parabolic trough mirror systems is the use of “Fresnel reflectors”. These reflectors make use of the Fresnel lens effect, which allows for a concentrating mirror with a large aperture and short focal length while reducing the volume of material required for the reflector. This greatly reduces the system’s cost because of its parabolic reflectors are typically very expensive. [2] However, in recent years thin-film nanotechnology has significantly reduced the cost of parabolic mirrors.[6]

A major challenge that must be addressed in any solar concentrating technology is the changing angle of the incident rays of the sunlight striking the mirrors as the sun progresses throughout the day. The reflectors of a CLFR are typically aligned in a north-south orientation and turn to a single axis using a computer controlled solar tracker system. [7] This allows the system to maintain the proper angle of incidence between sun rays and mirrors, thus optimizing energy transfer.

Absorbers

The absorb is located at the focal line of the mirrors. It runs parallel to and above the reflector segments to transport radiation into some working thermal fluid. The basic design of the absorber for the CLFR system is an inverted air cavity with a blanket enclosing insulated steam tubes, shown in Fig.2. This design has been proven to be simple and effective with good optical and thermal performance. [1]

For optimum performance of the CLFR, several design factors must be optimized.

  • First, heat transfer between the absorbent and the thermal fluid must be maximized. [1] This link is on the surface of the steam tubes being selective. A selective surface optimizes the ratio of energy absorbed to energy emitted. Acceptable surfaces absorb 96% of incident radiation while emitting only 7% through infra-red radiation. [8] Electro-chemically deposited black chromium is used for its ample performance and ability to withstand high temperatures. [1]
  • Second, the absorber must be designed so that the temperature distribution across the selective surface is uniform. Non-uniform temperature distribution leads to accelerated degradation of the surface. Typically, a uniform temperature of 300 ° C (573 K, 572 ° F) is desired. [1] Uniform distributions are obtained by changing the temperature of the insulation and the size of the cavity.

As opposed to the traditional LFR, the CLFR makes use of multiple absorbers within the vicinity of its mirrors. These additional absorbers allow the mirrors to alternate their inclination, as illustrated in Fig. 3. This arrangement is advantageous for several reasons.

  • First, alternating inclinations the effect of reflectors blocking adjacent reflectors’ access to sunlight, improving the system’s efficiency.
  • Second, multiple absorbers minimizes the amount of ground required for installation. This in turn is getting ready and ready. [1]
  • Finally, having the panels in close proximity reduces the length of the absorptions, which decreases both by the absorb lines and the overall cost of the system.

Applications

In March 2009, the German company Novatec Biosol constructed a Fresnel solar power plant Known As PE 1. The solar thermal power plant uses a standard linear Fresnel optical design (not CLFR) and HAS an electrical capacity of 1.4 MW. PE 1, 18,000 m 2 (1.8 ha, 4.4 acres). [9] The steam is generated by concentrating sunlight directly onto a linear receiver, which is 7.40 meters (24.28 ft) above the ground. [9] An absorbing tube is located in the focal line of the mirror field where water is heated to 270 ° C (543 K; 518 ° F) saturated steam. This steam in turn powers a generator. [9]

The commercial success of the PE 1 has led Novatec Solar to design has 30 MW solar power plant known as PE 2. PE 2 is in commercial operation since 2012. [10]

From 2013 on Novatec Solar developed a molten salt system in cooperation with BASF . [11] It is used as a heat transfer fluid in the collector which is directly transferred to a thermal energy storage. A salt temperature of up to 550 ° C (823 K, 1,022 ° F) facilitates the production of a standard turbine for electricity generation , enhanced oil recovery or desalination . A molten salt demonstration plant was realized on PE 1 to proof the technology. Since 2015 FRENELL GmbH, a management buy-out of Novatec Solar took over the commercial development of the direct molten salt technology.

In April 2008, the solar thermal company AREVA Solar (Ausra) opened a large factory in Las Vegas, Nevada that will produce linear Fresnel reflectors. [12] The factory will be capable of producing enough solar collectors to provide 200 MW of power per month. [13]

AREVA Solar (Ausra) has finished construction of the 5 MW Kimberlina Solar Thermal Energy Plant in Bakersfield, California. [13] This is the first commercial linear Fresnel reflector plant in the United States. The solar collectors were produced at the Ausra factory in Las Vegas.

AREVA Solar (Ausra) also operates a linear fresnel reflector plant in New South Wales, Australia. This reflector plant supplements the 2,000 MW coal-fired Liddell Power Station. [14] The power generated by the solar thermal system is used to provide electricity for the plant’s operation, offsetting the plant’s internal power usage.

Solar Fire, a suitable technology NGO in India, has developed an open source design for a small, manually operated, 12kW peak Fresnel concentrator that is up to 750 ° C (1,020 K; 1,380 ° F) and can be used for various thermal applications including steam powered electricity generation. [15] [16]

The largest CSP systems using Compact linear Fresnel reflector technology include the 125 MW Reliance Areva CSP plant in India. [17]

See also

  • Concentrating solar power
  • List of Solar Thermal Power Stations
  • Solar energy
  • Solar thermal energy

References

  1. ^ Jump up to:a b c d e f g Dey, CJ (2004). “Heat transfer aspect of an elevated linear absorber”. Solar Energy . 76 : 243-249. doi : 10.1016 / j.solener.2003.08.030 .
  2. ^ Jump up to:a b c Mills, DR (2004). “Advances in solar thermal electricity technology”. Solar Energy . 76 : 19-31. doi : 10.1016 / S0038-092X (03) 00102-6 .
  3. Jump up^ Philipp Schramek and David R. Mills,Multi-tower Solar Array, Solar Energy 75, pp. 249-260, 2003
  4. Jump up^ Chaves, Julio (2015). Introduction to Nonimaging Optics, Second Edition . CRC Press . ISBN  978-1482206739 .
  5. Jump up^ Julio Chaves and Manuel Collares-Pereira,Extended-matched two-stage concentrators with multiple receivers, Solar Energy 84, pp. 196-207, 2010
  6. Jump up^ United States Department of Energy (2009). “Solar Energy Technologies Program: Concentrating Solar Power” ( PDF ) .
  7. Jump up^ Mills, DR; Morrison, Graham L. (2000). “Compact linear Fresnel solar thermal reflector power plants”. Solar Energy . 68 (3): 263-283. doi :10.1016 / S0038-092X (99) 00068-7 .
  8. Jump up^ “SolMax, Solar Selective Surface Foil” ( PDF ) .
  9. ^ Jump up to:a b c “World First in Solar Power Plant Technology” .
  10. Jump up^ “Home” . www.puertoerrado2.com . October 27, 2011.
  11. Jump up^ “Novatec Solar and BASF nehmen solarthermische Demonstrations-anlage mit neuartiger Flüssigsalz-Technologie in Betrieb” .
  12. Jump up^ Schlesinger, V. (July 2008). “Solar Thermal Power Just Got Hotter”. Plenty Magazine
  13. ^ Jump up to:a b “Ausra Technology” .
  14. Jump up^ Jahanshahi, M. (August 2008). “Liddell Thermal Power Station – Greening Coal-fired Power”. EcoGeneration
  15. Jump up^ Parmar, Vijaysinh (Feb 5, 2011). ” ‘ Solar fire’ to quench thirst at grassroots energy” . Times of India . Retrieved May 15, 2011 .
  16. Jump up^ “Solar Fire P32 – Solar Fire Project” . solarfire.org . 2011 . Retrieved May 15, 2011 .
  17. Jump up^ Purohit, I. Purohit, P. 2017. Technical and economic potential of concentrating solar thermal power generation in India. Renewable and Sustainable Energy Reviews, 78, pp. 648-667,doi:10.1016 / j.rser.2017.04.059.

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